Sometimes the terms 'dynamic' and 'static' are used.[citation needed] 'Dynamic' exercises such as steady running, tend to produce a lowering of the diastolic blood pressure during exercise, due to the improved blood flow. Conversely, static exercise (such as weight-lifting) can cause the systolic pressure to rise significantly (during the exercise).[citation needed]

Health effects

Physical exercise is important for maintaining physical fitness and can contribute positively to maintaining a healthy weight, building and maintaining healthy bone density, muscle strength, and joint mobility, promoting physiological well-being, reducing surgical risks, and strengthening the immune system. Developing research has demonstrated that many of the benefits of exercise are mediated through the role of skeletal muscle as an endocrine organ. That is, contracting muscles release multiple substances known as myokines which promote the growth of new tissue, tissue repair, and multiple anti-inflammatory functions, which in turn reduce the risk of developing various inflammatory diseases.[13]

Exercise reduces levels of cortisol,[14] which causes many health problems, both physical and mental.[15] Conversely, exercise increases levels of saliva nitrite, which can be converted to the nitric oxide, thereby, increasing intensity and training load. Saliva testing for nitric oxide serves as a marker for training status.[16]

Endurance exercise before meals lowers blood glucose more than the same exercise after meals.[17] According to the World Health Organization, lack of physical activity contributes to approximately 17% of heart disease and diabetes, 12% of falls in the elderly, and 10% of breast cancer and colon cancer.[18]

There is evidence that vigorous exercise (90–95% of VO2 Max) induces a greater degree of physiological cardiac hypertrophy than moderate exercise (40 to 70% of VO2 Max), but it is unknown whether this has any effects on overall morbidity and/or mortality.[19]

Both aerobic and anaerobic exercise work to increase the mechanical efficiency of the heart by increasing cardiac volume (aerobic exercise), or myocardial thickness (strength training). Ventricular hypertrophy, the thickening of the ventricular walls, is generally beneficial and healthy if it occurs in response to exercise.

Not everyone benefits equally from exercise. There is tremendous variation in individual response to training; where most people will see a moderate increase in endurance from aerobic exercise, some individuals will as much as double their oxygen uptake, while others can never augment endurance.[20][21] However, muscle hypertrophy from resistance training is primarily determined by diet and testosterone.[22] This genetic variation in improvement from training is one of the key physiological differences between elite athletes and the larger population.[23][24] Studies have shown that exercising in middle age leads to better physical ability later in life.[25]

Cardiovascular system

The beneficial effect of exercise on the cardiovascular system is well documented. There is a direct relation between physical inactivity and cardiovascular mortality, and physical inactivity is an independent risk factor for the development of coronary artery disease. There is a dose-response relation between the amount of exercise performed from approximately 700 to 2000 kcal of energy expenditure per week and all-cause mortality and cardiovascular disease mortality in middle-aged and elderly populations. The greatest potential for reduced mortality is in the sedentary who become moderately active. Most beneficial effects of physical activity on cardiovascular disease mortality can be attained through moderate-intensity activity (40% to 60% of maximal oxygen uptake, depending on age). ... persons who modify their behavior after myocardial infarction to include regular exercise have improved rates of survival. ... Persons who remain sedentary have the highest risk for all-cause and cardiovascular disease mortality.[26]

Immune system

Although there have been hundreds of studies on exercise and the immune system, there is little direct evidence on its connection to illness. Epidemiological evidence suggests that moderate exercise has a beneficial effect on the human immune system; an effect which is modeled in a J curve. Moderate exercise has been associated with a 29% decreased incidence of upper respiratory tract infections (URTI), but studies of marathon runners found that their prolonged high-intensity exercise was associated with an increased risk of infection occurrence. However, another study did not find the effect. Immune cell functions are impaired following acute sessions of prolonged, high-intensity exercise, and some studies have found that athletes are at a higher risk for infections. The immune systems of athletes and nonathletes are generally similar. Athletes may have slightly elevated natural killer cell count and cytolytic action, but these are unlikely to be clinically significant.[27]

Vitamin C supplementation has been associated with lower incidence of URTIs in marathon runners.[27]

Biomarkers of inflammation such as C-reactive protein, which are associated with chronic diseases, are reduced in active individuals relative to sedentary individuals, and the positive effects of exercise may be due to its anti-inflammatory effects. In individuals with heart disease, exercise interventions lower blood levels of fibrinogen and C-reactive protein, an important cardiovascular risk marker.[28] The depression in the immune system following acute bouts of exercise may be one of the mechanisms for this anti-inflammatory effect.[27]

Cancer

A systematic review evaluated 45 studies that examined the relationship between physical activity and cancer survivorship. According to the study results "There was consistent evidence from 27 observational studies that physical activity is associated with reduced all-cause, breast cancer–specific, and colon cancer–specific mortality".[29]

Epigenetic effects

Physical exercise was correlated with a lower methylation frequency of two tumor suppressor genes, CACNA2D3 and L3MBTL.[30][31] Hypermethylation of CACNA2D3 is associated with gastric cancer, while hypermethylation of L3MBTL is associated with breast cancer, brain tumors and hematological malignancies.[30][31][32][33] A recent study proposed that "DNA methylation may be a mechanism linking exercise and cancer incidence and could serve as a biomarker for behavioral intervention trials. Studies with larger samples, objectively measured exercise, and more cancer-related markers are needed". According to the study, "Individuals who were more physically fit and who exercised more minutes per week had lower levels of DNA methylation. Those who increased their minutes of physical activity over 12 months experienced decreases in DNA methylation."[34]

Cancer cachexia

Physical exercise is becoming a widely accepted non-pharmacological intervention for the prevention and attenuation of cancer cachexia.[35] "Cachexia is a multiorganic syndrome associated with cancer, characterized by inflammation, body weight loss (at least 5%) and muscle and adipose tissue wasting".[36] The exercise-induced transcription coactivator peroxisome proliferator-activated receptor-γ coactivator 1α (PGC1α) (see PPARGC1A), which suppresses FOXO and NF-κB dependent transcription during atrophy induced by fasting or denervation, may be a key intermediate responsible for the benficial antiatrophic effects of physical exercise on cancer cachexia.[37][38] The exercise-induced isoform PGC1α4, which can repress myostatin and induce IGF1 and hypertrophy, is a potential drug target for treatment of cancer cachexia.[39] Other factors, such as JUNB and SIRT1, that maintain skeletal muscle mass and promote hypertrophy are also induced with regular physical exercise.[40][41]

Brain function

Physical activity has been shown to be neuroprotective in many neurodegenerative and neuromuscular diseases.[42] Evidence suggests that it reduces the risk of developing dementia.[43] The Caerphilly Heart Disease Study followed 2,375 male subjects over 30 years and examined the association between regular physical exercise and dementia. The study found that men who exercised regularly had a 59% reduction in dementia when compared to the men who didn't exercise.[44]

In mice, exercise improves cognitive functioning via improvement of spatial learning, and enhancement of synaptic plasticity and neurogenesis.[46] In a 2009 study, scientists made two groups of mice swim a water maze, and then in a separate trial subjected them to an unpleasant stimulus to see how quickly they would learn to move away from it. Then, over the next four weeks they allowed one group of mice to run inside their rodent wheels, an activity most mice enjoy, while they forced the other group to work harder on mini-treadmills at a speed and duration controlled by the scientists. They then tested both groups again to track their learning skills and memory. Both groups of mice improved their performances in the water maze from the earlier trial. But only the extra-worked treadmill runners were better in the avoidance task, a skill that, according to neuroscientists, demands a more complicated cognitive response.[47]

The mice who were forced to run on the treadmills showed evidence of molecular changes in several portions of their brains when viewed under a microscope, while the voluntary wheel-runners had changes in only one area. According to an author of the study, "our results support the notion that different forms of exercise induce neuroplasticity changes in different brain regions."[48]

Physical activity is thought to have other beneficial effects related to cognition as it increases levels of nerve growth factors, which support the survival and growth of a number of neuronal cells.[53]

Sleep

A 2010 review of published scientific research suggested that exercise generally improves sleep for most people, and helps sleep disorders such as insomnia. The optimum time to exercise may be 4 to 8 hours before bedtime, though exercise at any time of day is beneficial, with the possible exception of heavy exercise taken shortly before bedtime, which may disturb sleep. There is, in any case, insufficient evidence to draw detailed conclusions about the relationship between exercise and sleep.[64]

According to a 2005 study, exercise is the most recommended alternative to sleeping pills for resolving insomnia. Sleeping pills are more costly than to make time for a daily routine of staying fit, and may have dangerous side effects in the long run. Exercise can be a healthy, safe and inexpensive way to achieve more and better sleep.[65]

Excessive exercise

Too much exercise can be harmful. Without proper rest, the chance of stroke or other circulation problems increases,[66] and muscle tissue may develop slowly. Extremely intense, long-term cardiovascular exercise, as can be seen in athletes who train for multiple marathons, has been associated with scarring of the heart and heart rhythm abnormalities.[67][68][69]

Inappropriate exercise can do more harm than good, with the definition of "inappropriate" varying according to the individual. For many activities, especially running and cycling, there are significant injuries that occur with poorly regimented exercise schedules. Injuries from accidents also remain a major concern,[70] whereas the effects of increased exposure to air pollution seem only a minor concern.[71][72]

In extreme instances, over-exercising induces serious performance loss. Unaccustomed overexertion of muscles leads to rhabdomyolysis (damage to muscle) most often seen in new army recruits.[73] Another danger is overtraining, in which the intensity or volume of training exceeds the body's capacity to recover between bouts. One sign of Overtraining Syndrome (OTS) is suppressed immune function, with an increased incidence of upper respiratory tract infection (URTI). An increased incidence of URTIs is also associated with high volume/intensity training, as well as with excessive exercise (EE), such as in a marathon.[74]

Stopping excessive exercise suddenly may create a change in mood. Feelings of depression and agitation can occur when withdrawal from the natural endorphins produced by exercise occurs.[citation needed] Exercise should be controlled by each body's inherent limitations. While one set of joints and muscles may have the tolerance to withstand multiple marathons, another body may be damaged by 20 minutes of light jogging. This must be determined for each individual.

Too much exercise may cause a woman to miss her period, a symptom known as amenorrhea.[75] This is a very serious condition which indicates a woman is pushing her body beyond its natural boundaries.[76]

Myokine research

In a 2012 article regarding myokine research, Pedersen and Febbraio concluded that "physical inactivity and muscle disuse lead to loss of muscle mass and accumulation of visceral adipose tissue and consequently to the activation of a network of inflammatory pathways, which promote development of insulin resistance, atherosclerosis, neurodegeneration and tumour growth and, thereby, promote the development of a cluster of chronic diseases. By contrast, the finding that muscles produce and release myokines provides a molecular basis for understanding how physical activity could protect against premature mortality.... Physical inactivity or muscle disuse potentially leads to an altered or impaired myokine response and/or resistance to the effects of myokines, which explains why lack of physical activity increases the risk of a whole network of diseases, including cardiovascular diseases, T2DM (Type 2 Diabetes Mellitus), cancer and osteoporosis."[77]

Public health measures

As of 2011 the effects of community wide interventions to increase exercise levels at the population level is unknown.[78] Signs that encourage the use of stairs, as well as community campaigns, may increase exercise levels.[79] The city of Bogotá, Colombia, for example, blocks off 113 kilometers (70 mi) of roads on Sundays and holidays to make it easier for its citizens to get exercise. These pedestrian zones are part of an effort to combat chronic diseases, including obesity.[80]

Exercise trends

Worldwide there has been a large shift towards less physically demanding work.[81] This has been accompanied by increasing use of mechanized transportation, a greater prevalence of labor saving technology in the home, and less active recreational pursuits.[81]Personal lifestyle changes however can correct the lack of physical exercise.

New research indicate integrating mindfulness to physical exercise interventions increase exercise adherence, self-efficacy and also has positive effects both psychologically and physiologically.[82]

Nutrition and recovery

Proper nutrition is as important to health as exercise. When exercising, it becomes even more important to have a good diet to ensure that the body has the correct ratio of macronutrients while providing ample micronutrients, in order to aid the body with the recovery process following strenuous exercise.[83]

History

The benefits of exercise have been known since antiquity. Marcus Cicero, around 65 BC, stated: "It is exercise alone that supports the spirits, and keeps the mind in vigor."[84]

Several mass exercise movements were started in the early twentieth century to realise the benefits of exercise. The first and most significant of these in the UK was the Women's League of Health and Beauty founded in 1930 by Mary Bagot Stack that had 166,000 members in 1937.[85]

However, the link between physical health and exercise (or lack of it) was only discovered in 1949 and reported in 1953 by a team led by Jerry Morris.[86][87] Dr. Morris noted that men of similar social class and occupation (bus conductors versus bus drivers) had markedly different rates of heart attacks, depending on the level of exercise they got: bus drivers had a sedentary occupation and a higher incidence of heart disease, while bus conductors were forced to move continually and had a lower incidence of heart disease.[87] This link had not previously been noted and was later confirmed by other researchers.

In other animals

Physical exercise has been shown to benefit a wide range of other mammals, as well as salmon, juvenile crocodiles, and at least one species of bird.[88]

However, several studies have shown that lizards display no benefit from exercise, leading them to be termed "metabolically inflexible".[89]

A number of studies of both rodents and humans have demonstrated that individual differences in both ability and propensity for exercise (i.e., voluntary exercise) have some genetic basis.[90][91]

^Parker-Pope, T. (2001). For a Healthy Brain You Really Need to Use Your Head -- Physical and Mental Exercise Can Stave Off Mental Decline. The Wall Street Journal Europe, November 26, 2001, 8. Retrieved October 5, 2006, from ProQuest database.

^ abcCooney GM, Dwan K, Greig CA, Lawlor DA, Rimer J, Waugh FR, McMurdo M, Mead GE (2013). "Exercise for depression". Cochrane Database Syst Rev9: CD004366. doi:10.1002/14651858.CD004366.pub6. PMID24026850. Exercise is moderately more effective than a control intervention for reducing symptoms of depression, but analysis of methodologically robust trials only shows a smaller effect in favour of exercise. When compared to psychological or pharmacological therapies, exercise appears to be no more effective, though this conclusion is based on a few small trials.

^ abcdMura G, Moro MF, Patten SB, Carta MG (2014). "Exercise as an add-on strategy for the treatment of major depressive disorder: a systematic review". CNS Spectr19 (6): 496–508. doi:10.1017/S1092852913000953. PMID24589012. Considered overall, the studies included in the present review showed a strong effectiveness of exercise combined with antidepressants. ... Conclusions
This is the first review to have focused on exercise as an add-on strategy in the treatment of MDD. Our findings corroborate some previous observations that were based on few studies and which were difficult to generalize.41,51,73,92,93 Given the results of the present article, it seems that exercise might be an effective strategy to enhance the antidepressant effect of medication treatments. Moreover, we hypothesize that the main role of exercise on treatment-resistant depression is in inducing neurogenesis by increasing BDNF expression, as was demonstrated by several recent studies.

^ abcJosefsson T, Lindwall M, Archer T (2014). "Physical exercise intervention in depressive disorders: meta-analysis and systematic review". Scand J Med Sci Sports24 (2): 259–272. doi:10.1111/sms.12050. PMID23362828. Physical activity has also become increasingly and firmly associated with improvements in mental health and psychological well-being (Mutrie, 2000; Landers & Arent, 2007). In particular, exercise is believed to be effective in preventing depression and also to significantly reduce depressive symptoms in clinical as well as in nonclinical populations (O'Neal et al., 2000; Landers & Arent, 2007). Several correlational studies show that exercise is negatively related to depressive symptoms (e.g., Galper et al., 2006; Hassmén et al., 2000). Moreover, a considerably large number of intervention studies have by now investigated the effect of various exercise programs on depression and the vast majority of them indicate that exercise significantly reduces depression (e.g., Blumenthal et al., 2007; Martinsen et al., 1985; Singh et al., 1997). ... To date, it is not possible to determine exactly how effective exercise is in reducing depression symptoms in clinical and nonclinical depressed populations, respectively. However, the results from the present meta-analysis as well as from seven earlier meta-analyses (North et al., 1990; Craft & Landers, 1998; Lawlor & Hopker, 2001; Stathopoulou et al., 2006; Mead et al., 2009; Rethorst et al., 2009; Krogh et al., 2011) indicate that exercise has a moderate to large antidepressant effect. Some meta-analytic results (e.g., Rethorst et al., 2009) suggest that exercise may be even more efficacious for clinically depressed people. ... In short, our final conclusion is that exercise may well be recommended for people with mild and moderate depression who are willing, motivated, and physically healthy enough to engage in such a program.

^ abcRosenbaum S, Tiedemann A, Sherrington C, Curtis J, Ward PB (2014). "Physical activity interventions for people with mental illness: a systematic review and meta-analysis". J Clin Psychiatry75 (9): 964–974. doi:10.4088/JCP.13r08765. PMID24813261. This systematic review and meta-analysis found that physical activity reduced depressive symptoms among people with a psychiatric illness. The current meta-analysis differs from previous studies, as it included participants with depressive symptoms with a variety of psychiatric diagnoses (except dysthymia and eating disorders). ... This review provides strong evidence for the antidepressant effect of physical activity; however, the optimal exercise modality, volume, and intensity remain to be determined. ... Conclusion
Few interventions exist whereby patients can hope to achieve improvements in both psychiatric symptoms and physical health simultaneously without significant risks of adverse effects. Physical activity offers substantial promise for improving outcomes for people living with mental illness, and the inclusion of physical activity and exercise programs within treatment facilities is warranted given the results of this review.

^ abTantimonaco M, Ceci R, Sabatini S, Catani MV, Rossi A, Gasperi V, Maccarrone M (2014). "Physical activity and the endocannabinoid system: an overview". Cell. Mol. Life Sci.71 (14): 2681–2698. doi:10.1007/s00018-014-1575-6. PMID24526057. The traditional view that PA engages the monoaminergic and endorphinergic systems has been challenged by the discovery of the endocannabinoid system (ECS), composed of endogenous lipids, their target receptors, and metabolic enzymes. Indeed, direct and indirect evidence suggests that the ECS might mediate some of the PA-triggered effects throughout the body. ... the evidence that PA induces some of the psychotropic effects elicited by the Cannabis sativa active ingredient Δ9-tetrahydrocannabinol (Δ9-THC, Fig. 1), like bliss, euphoria, and peacefulness, strengthened the hypothesis that endocannabinoids (eCBs) might mediate, at least in part, the central and peripheral effects of exercise [14]. ... To our knowledge, the first experimental study aimed at investigating the influence of PA on ECS in humans was carried out in 2003 by Sparling and coworkers [63], who showed increased plasma AEA content after 45 min of moderate intensity exercise on a treadmill or cycle ergometer. Since then, other human studies have shown increased blood concentrations of AEA ... A dependence of the increase of AEA concentration on exercise intensity has also been documented. Plasma levels of AEA significantly increased upon 30 min of moderate exercise (heart rate of 72 and 83 %), but not at lower and significantly higher exercise intensities, where the age-adjusted maximal heart rate was 44 and 92 %, respectively ... Several experimental data support the hypothesis that ECS might, at least in part, explain PA effects on brain functions, because: (1) CB1 is the most abundant GPCR in the brain participating in neuronal plasticity [18]; (2) eCBs are involved in several brain responses that greatly overlap with the positive effects of exercise; (3) eCBs are able to cross the blood–brain barrier [95]; and (4) exercise increases eCB plasma levels [64–67].

^ abDinas PC, Koutedakis Y, Flouris AD (2011). "Effects of exercise and physical activity on depression". Ir J Med Sci180 (2): 319–325. doi:10.1007/s11845-010-0633-9. PMID21076975. According to the 'endorphins hypothesis', exercise augments the secretion of endogenous opioid peptides in the brain, reducing pain and causing general euphoria. ... Based upon a large effect size, the results confirmed the endorphins hypothesis demonstrating that exercise leads to an increased secretion of endorphins which, in turn, improved mood states.
β-Endorphin, an endogenous μ-opioid receptor selective ligand, has received much attention in the literature linking endorphins and depression or mood states. ... exercise of sufficient intensity and duration can increase circulating β-endorphin levels. ... Moreover, a recent study demonstrated that exercise and physical activity increased β-endorphin levels in plasma with positive effects on mood. Interestingly, the researchers reported that, independently of sex and age, dynamic anaerobic exercises increased β-endorphin, while resistance and aerobic exercises seem to only have small effects on β-endorphins. ... The results showed that mood tends to be higher in a day an individual exercises as well as that daily activity and exercise overall are strongly linked with mood states. In line with these findings, a recent study showed that exercise significantly improved mood states in non-exercises, recreational exercisers, as well as marathon runners. More importantly, the effects of exercise on mood were twofold in recreational exercisers and marathon runners.

^ abSzabo A, Billett E, Turner J (2001). "Phenylethylamine, a possible link to the antidepressant effects of exercise?". Br J Sports Med35 (5): 342–343. doi:10.1136/bjsm.35.5.342. PMC1724404. PMID11579070. The 24 hour mean urinary concentration of phenylacetic acid was increased by 77% after exercise. ... These results show substantial increases in urinary phenylacetic acid levels 24 hours after moderate to high intensity aerobic exercise. As phenylacetic acid reflects phenylethylamine levels3 , and the latter has antidepressant effects, the antidepressant effects of exercise appear to be linked to increased phenylethylamine concentrations. Furthermore, considering the structural and pharmacological analogy between amphetamines and phenylethylamine, it is conceivable that phenylethylamine plays a role in the commonly reported "runners high" thought to be linked to cerebral β-endorphin activity. The substantial increase in phenylacetic acid excretion in this study implies that phenylethylamine levels are affected by exercise. ... A 30 minute bout of moderate to high intensity aerobic exercise increases phenylacetic acid levels in healthy regularly exercising men. The findings may be linked to the antidepressant effects of exercise.

^Erickson KI, Miller DL, Roecklein KA (2012). "The aging hippocampus: interactions between exercise, depression, and BDNF". Neuroscientist18 (1): 82–97. doi:10.1177/1073858410397054. PMC3575139. PMID21531985. Late adulthood is associated with increased hippocampal atrophy and dysfunction. ... However, there is strong evidence that decreased BDNF is associated with age-related hippocampal dysfunction, memory impairment, and increased risk for depression, whereas increasing BDNF by aerobic exercise appears to ameliorate hippocampal atrophy, improve memory function, and reduce depression. ... For example, longitudinal studies have reported between 1% and 2% annual hippocampal atrophy in adults older than 55 years without dementia ... Over a nine-year period, greater amounts of physical activity in the form of walking are associated with greater gray matter volume in several regions including prefrontal, temporal, and hippocampal areas. ... The prefrontal cortex and hippocampus deteriorate in late adulthood, preceding and leading to deficits in executive and memory function. We examined in this review the evidence that age-related changes in BDNF might at least partially explain hippocampal atrophy and increased risk for memory impairment. We can conclude that 1) decreases in BDNF protein expression are associated with poorer hippocampal function and increased rates of geriatric depression and AD. ... 3) Aerobic exercise enhances executive and memory function and reduces hippocampal atrophy in late adulthood, and this may be partially mediated through a BDNF pathway.

^Lindemann L, Hoener MC (2005). "A renaissance in trace amines inspired by a novel GPCR family". Trends Pharmacol. Sci.26 (5): 274–281. doi:10.1016/j.tips.2005.03.007. PMID15860375. The pharmacology of TAs might also contribute to a molecular understanding of the well-recognized antidepressant effect of physical exercise [51]. In addition to the various beneficial effects for brain function mainly attributed to an upregulation of peptide growth factors [52,53], exercise induces a rapidly enhanced excretion of the main β-PEA metabolite β-phenylacetic acid (b-PAA) by on average 77%, compared with resting control subjects [54], which mirrors increased β-PEA synthesis in view of its limited endogenous pool half-life of ~30 s [18,55].

^Berry MD (2007). "The potential of trace amines and their receptors for treating neurological and psychiatric diseases". Rev Recent Clin Trials2 (1): 3–19. doi:10.2174/157488707779318107. PMID18473983. It has also been suggested that the antidepressant effects of exercise are due to an exercise-induced elevation of PE [151].